Current leadthrough for a vacuum pump

ABSTRACT

The vacuum pump comprises a casing ( 10 ) closed by a vacuum cover ( 20 ). Between an end wall ( 14 ) of the casing ( 10 ) and the vacuum cover ( 20 ), a circuit board ( 16 ) is arranged for current feedthrough. The circuit board ( 16 ) is sealed by two sealing elements ( 15, 21 ) of different diameters so that an annular partial region ( 22 ) is on its outer side subjected to the atmospheric pressure and is on its inner side subjected to the vacuum. It is avoided that the circuit board ( 16 ) laterally projects beyond the contour of the casing ( 10 ).

The present invention relates to a vacuum pump comprising a vacuum-tight casing accommodating a motor and a pump rotor, and further comprising a current feedthrough including a circuit board.

Vacuum pumps in the form of turbomolecular pumps comprise a rotor which is configured to rotate at very high rotational numbers and thus is adapted to generate a high vacuum. In many pumps of this type, the rotor and the motor for driving the rotor are supported in magnetic bearings. Within the casing, a vacuum prevails, usually in the range below 10 mbar. The current feedthrough devices for the motor and for the vacuum bearings are provided in a vacuum-tight arrangement on the casing.

EP 1 757 825 A1 describes a vacuum pump wherein the current feedthrough into the casing comprises a circuit board. An inner side of the circuit board is arranged in abutment on the casing with interposition of a sealing means, and an outer side is arranged in abutment on an outer vacuum cover with interposition of a further sealing means, said vacuum cover closing the casing in a vacuum-tight manner. The traces of the circuit board are guided through the gap between the two sealing means. The circuit board comprises a projecting portion arranged externally of the casing and provided with a connector. A further connector is arranged in contact with the traces within the casing.

It is an object of the invention to provide a vacuum pump wherein the current feedthrough device does not comprise circuit board portions projecting beyond the casing, thus avoiding the risk of damage to the circuit board and to exposed plug devices.

The vacuum pump according to the present invention is defined by claim 1. Said vacuum pump is provided with a circuit board having a first sealing means and a second sealing means arranged thereon, the first sealing means and the second sealing means being positioned with a lateral displacement relative to each other so that a partial region of the circuit board is on its outer side subjected to the atmospheric pressure and is on its inner side subjected to the generated vacuum.

An advantage herein resides in that said partial region which is exposed to a pressure difference and does not laterally extend beyond the wall of the casing, can be used to connect electric conductors to the board. Due to the lateral displacement of the sealing means relative to each other, a space is created within the wall contour which will be available for connection of external lines. Consequently, this obviates the need for the circuit board to extend beyond the outer contour of the casing. In that wall portion of the circuit board where the pressure difference is effective, it is the circuit board itself that forms the wall of the pump. Deflection in this partial region is prevented because the circuit board is given support by abutment on the front-side end of the wall of the casing.

According to a preferred embodiment of the invention, the vacuum cover forming the vacuum closure of the casing is arranged within a protective cover and is movable relative thereto. The possibility of movement vertically to the plane of the cover will allow for the sealing means to be pressed into position. The vacuum cover is held in place by the pressure difference acting on it and is only loosely positioned by the protective cover. The protective cover serves for avoiding damage to the vacuum cover and the circuit board. Apart from this function, the protective cover is useful as a support for a plug connection of the external electric lines leading to the circuit board. The protective cover includes a positioning means for positioning the vacuum cover but, on the other hand, does permit the vacuum cover to undergo reactions to the existing pressure difference. Alternatively, it is possible to form the vacuum cover integrally with the protective cover.

Embodiments of the invention will be explained in greater detail hereunder with reference to the accompanying drawings.

FIG. 1 is a partly sectional longitudinal view of the casing of a vacuum pump, illustrating a first embodiment of the current feedthrough, and

FIG. 2 is a view of a second embodiment of the current feedthrough wherein the circuit board is additionally provided with electric components.

In FIG. 1, the casing 10 of a turbomolecular pump is illustrated. Located within casing 10 are a motor and a pump rotor. Casing 10 is provided with a pump inlet 11 on one of its ends and with a pump outlet 12 on its circumference. At said pump inlet 11, the vacuum is generated. Said pump outlet 12 can lead to the atmosphere or to a pre-vacuum pump.

At the rear end of an annular wall 13 of the casing, a planar end face 14 is arranged. End face 14 is formed with a groove accommodating an annular first sealing means 15 shaped as an O-ring. Arranged in abutment on end face 14 is a circuit board 16 consisting of a body of insulating material provided with traces (not shown) on one or both of its sides. Such circuit boards are also referred to as “printed circuits”. Circuit board 16 is arranged in sealing abutment on sealing means 15. In the central area of the circuit board, which is surrounded by end face 14, an opening 17 is formed in the board for pressure compensation. Circuit board 16 has an inner side 18 facing towards the interior chamber of the pump, and an outer side 19 facing away from the interior chamber. Said inner side 18 is arranged in abutment with the first sealing means 15.

A vacuum cover 20 is set against the outer side 19 of the circuit board. The vacuum cover comprises an annular groove with a second sealing means 21 held therein. Also this sealing means is an annular sealing in the form of an O-ring. The second sealing means 21 has a smaller opening diameter than the first sealing means 15. Between the two sealing means 15,21, there is thus generated an annular partial region 22 which is exposed to the existing pressure difference since its outer side is subjected to the atmospheric pressure and its inner side is subjected to the vacuum. Because of the provision of opening 17, a balanced pressure prevails in the region enclosed by the second sealing means 21, i.e. the vacuum in the interior of the casing will in this region act on the vacuum cover 20. Thus, vacuum cover 20 is pressed in the direction toward wall 13 under the effect, of the atmospheric pressure.

On its front-side end, casing 10 is closed by a protective cover 23 which has no sealing function. Protective cover 23 includes a hollow space 24 for accommodating the vacuum cover 20, and a positioning means 25, formed as a stepped shoulder, for positioning the vacuum cover 20. The protective cover serves for protection of the vacuum cover as well as the circuit board and the elements connected thereto.

From the inner side 18 of circuit board 16, electric lines 26 extend into the interior of the casing. These lines can be power supply lines or also control or signal lines. The lines are connected to the conductor lines of the circuit board by soldering or plug attachment.

External electric conductors 27 are soldered or plugged to the outer side 19 of circuit board 16. Said conductors 27 are guided through the interior space 24 to a plug device 28 configured as an electrical multiple plug. Plug device 28 serves for connection of an external cable. The device is located on a side wall of protective cover 23 but could also be located on the rear surface.

Circuit board 16 does not laterally project beyond side wall 13. The partial region 22 between the sealing means 15 and 21 is provided as a connection region for the electric conductors 27.

The embodiment according to FIG. 2 is different from the embodiment according to FIG. 1 only in that the circuit board 16 is additionally provided with electrical components 30, such as e.g. resistors, capacitors, processors or memory devices. The components 30 can be passive and active components alike.

As in the first embodiment, vacuum cover 20 includes a recess which is enclosed by the edge supporting the sealing means 21. In FIG. 2, said recess 31 serves for accommodation of the components 30 fastened to the outer side 19 of the circuit board. 

1. A vacuum pump comprising a vacuum-tight casing, said casing accommodating a motor and a pump rotor and being provided with a pump inlet and a pump outlet, said pump further comprising a current feedthrough, said current feedthrough including a circuit board, an inner side of said circuit board being arranged in abutment on an end face of the wall of the casing with interposition of a first sealing means, and an outer side of said circuit board being arranged in abutment on a vacuum cover of the casing with interposition of a second sealing means, wherein said first and second sealing means are arranged with a lateral displacement relative to each other so that a partial region of the circuit board is on its outer side subjected to atmospheric pressure and is on its inner side subjected to a generated vacuum.
 2. The vacuum pump according to claim 1, further including external electric conductors extending from said partial region and connected to traces of the circuit board.
 3. The vacuum pump according to claim 2, wherein said external conductors are connected to a plug device fastened to the casing.
 4. The vacuum pump according to claim 1, wherein the vacuum cover is arranged in a protective cover and is movable relative thereto.
 5. The vacuum pump according to claim 4, wherein the protective cover is provided with a positioning means for positioning the vacuum cover.
 6. The vacuum pump according to claim 1, wherein the circuit board is formed with an opening for pressure compensation.
 7. The vacuum pump according to according to claim 1, wherein the circuit board carries electrical components on its inner side and/or its outer side.
 8. The vacuum pump according to claim 1, wherein the circuit board is provided with pump detection electronics.
 9. The vacuum pump according to claim 1, wherein the first and second sealing means are annular sealing elements with different opening diameters.
 10. The vacuum pump according to claim 3, wherein the plug device is mounted to a protective cover of the casing.
 11. The vacuum pump according to claim 3, wherein the first and second sealing means are first and second O-rings, the first O-ring being larger in diameter than the second O-ring.
 12. The vacuum pump according to claim 5, wherein the positioning means includes a shoulder of the protective cover.
 13. A vacuum pump comprising: a vacuum-tight casing, the casing holding a motor and a pump rotor and defining a pump inlet and a pump outlet; a circuit board, an inner side of said circuit board being arranged in abutment on an end face of the casing, and an outer side of said circuit board facing away from the end face of the casing: a vacuum cover covering a portion of the outer side of the circuit board and defining a hollow space therebetween; a first annular sealing element disposed between the casing end face and the circuit based inner side; a second annular sealing element being disposed between the circuit board outer face and the vacuum cover, the second annular sealing element being smaller than the first annular sealing element.
 14. The vacuum pump according to claim 13, wherein an opening is defined in the circuit board such that a pressure in the casing and a pressure in the hollow space between the vacuum cover and the circuit board outer side is balanced, such that a region of the circuit board outer side inside the second annular sealing element is subject to the pressure in the casing and a region of the circuit board outside of the second annular sealing element is subject to atmospheric pressure.
 15. The vacuum pump according to claim 14, wherein the pressure in the casing is a vacuum. 